SEOUL (AFP) - South Korean unionists and other activists have announced plans for a day of nationwide strikes and street rallies in protest at labour reforms and free trade negotiations with the United States.

Separately, a coalition of activist groups said an estimated 71,000 people would take to the streets of Seoul and 12 provincial cities on the same day to denounce the proposed free trade agreement (FTA) with the US.

"The government has chosen to ignore our voices or concerns. Therefore, we believe we have no alternative but to proceed with our plan to launch a full-fledged general strike," KCTU chief Jo Jun-Ho told a news conference.

He said tens of thousands of workers would walk out at the four major carmakers -- Hyundai Motor, Kia Motors, GM Daewoo and Ssangyong Motor -- for eight hours on Wednesday.

He said strikers would also include up to 10,000 unionized teachers, chemical industry workers and truckers. Strikers would stage a 15,000-strong rally in Seoul Wednesday and rallies are also planned in 15 provinces.

The KCTU, which launched a four-hour "warning" strike last week, has demanded the government's "sincere response" to its opposition to reforms aimed at making the labor market more flexible.

It said four-hour stoppages would be staged daily from November 23-28 and another eight-hour strike on November 29.

"The strike will continue indefinitely -- until the government gives a sincere response to our demands in a responsible manner," Jo said.

Hyundai Motor and its sister firm Kia Motors, the country's two biggest automakers, lost production of 2,500 cars due to the four-hour strike last week.

The auto industry is a key growth engine for the export-driven economy.

The KCTU claims a membership of 642,000 at 1,200 worksites.

It strongly opposes proposed labour reforms, including attempts to reduce disparities between "regular" workers on full contracts with unemployment, pension and health benefits, and irregular workers with far fewer benefits.

The government says the country needs a more flexible labour market and unions must accept gradual change.

The KCTU also opposes the FTA negotiations, as does an activist coalition called The Korean Alliance against the Korea-US FTA.

The coalition has told police that out of 71,000 demonstrators nationwide, some 5,000 are expected to rally in Seoul's city centre late Wednesday.

"We plan to mobilize some 7,800 riot police in Seoul alone to prevent the protest from turning violent," a National Police Agency official told AFP.

The coalition urged people to display banners, attach bumper stickers and sign petitions. It also asked South Koreans to join a boycott of US beef, which it says is being imported despite fears over mad cow disease.

President Roh Moo-Hyun's government has been pushing for the free trade pact despite strong opposition from farmers, workers and other activists who fear for their incomes and jobs.

In the last mass protests in July riot police used water cannon as some 70,000 people, including 13,000 farmers, rallied in downtown Seoul.

After a fourth round of talks last month, both sides expressed hope for an eventual deal even though the lengthy negotiations will drag on into next year.

A fifth round is scheduled for December in the United States and a sixth in South Korea in January.